This study will attempt to determine (i.e., map) the chromosomal location of the gene(s) responsible for the genetic susceptibility to migraine headaches using genetic analysis of 10-25 multi-generational families (100-300 subjects) that contain multiple members with migraine headache. International Headache Society criteria will be used to determine family members affected/unaffected by migraine. Linkage analysis will be performed by standard techniques of the core lab of Dr. Richard King on blood samples drawn from subjects.